This invention relates to intraluminal stent implants for maintaining patency of a body lumen in humans and animals and especially to such implants for use in blood vessels. The present invention comprises an improvement to stents which are generally cylindrical in shape and which are made up of a continuous winding such as that disclosed in U.S. Pat. No. 4,886,062 which is incorporated herein by reference. This type of stent is typically fitted over an inflatable element of a typical balloon catheter for implantation and is intended to act as a prosthesis stent which is implanted transluminally. This type of intravascular stent can be enlarged radially by inflation of the balloon after having been introduced percutaneously, transported transluminally and positioned at a desired location by means of the balloon catheter.
An important use of these stents is found in situations where part of the vessel wall or stenotic plaque blocks or occludes blood flow in the vessel. Dilation of the blood vessel is usually undertaken to correct a blood vessel occlusion i.e., a balloon catheter is utilized in a PTCA procedure to enlarge the occluded portion of the blood vessel. However, the dilation of the occlusion can form flaps, fissures and dissections which threaten re-closure of the dilated vessel. Implantation of a stent can provide support for such flaps and dissections and thereby prevent reclosure. However, such stents are not always easily removed or withdrawn.
In U.S. Pat. No. 5,019,090 issued to Pinchuk, a stent withdrawal procedure is disclosed in which a snare catheter is used to remove a stent. The snare catheter with a hook at its distal end is inserted into the blood vessel until the hook can snare a portion of the stent. The stent then uncoils as it is pulled from the blood vessel. However, this procedure cannot always be relied upon to withdraw the stent without injury to the blood vessel since it can be difficult to hook the expanded stent in a way that avoids damage to the blood vessel and also since the stent can easily become folded or crimped during the withdrawal procedure if the stent is hooked at an intermediate loop. It would therefore be desirable to provide a wire stent that can be applied to support flaps, fissures and dissections following angioplasty procedures and which also provides for simplified withdrawal when that support is no longer needed.